Energy storage – you can't do electric vehicles without it, and it sure would make renewable solar and wind energy a lot more useful.

That's the imperative behind 2009's push into energy storage – from the fast-moving world of batteries for electric and plug-in hybrid vehicles to the slower development of a variety of technologies for storing power on the electricity grid.

1. A123, Green Tech's First IPO of 2009: A123 Systems broke the green tech IPO drought in September, when it debuted its shares to the public markets and was immediately rewarded with a doubling of their price. But the lithium-ion battery maker has since seen shares fall to close to their initial offering price of $13.50, perhaps linked to the scaling back of electric vehicle plans by customer Chrysler. A123 is also making batteries for grid energy storage, bridging two worlds that have until now been mostly separate.

2. The Government Boosts Vehicle Batteries" Next-generation batteries wouldn't be where they are today without the billions of stimulus dollars the federal government has aimed at the sector. In August, the Department of Energy handed out $2.4 billion to such companies as EnerG2, A123 Systems, Johnson Controls, eTec, EnerDel, Saft and Chrysler and General Motors, most of it to build battery factories in the United States – a key goal of the grants, given Asia's dominance in battery technology and manufacturing.

3. Fuel Cells' Waning Fortunes? What the federal government has given to batteries, it has taken away from a once-favored alternative - fuel cells. Technologies to convert hydrogen into electricity and water are clean, but they also require a massive infrastructure to deliver hydrogen - which is mostly made today by cracking natural gas - to millions of vehicles. Energy Secretary Steven Chu has said he will cut back drastically on DOE funding for vehicular fuel cell research, which he described as decades away from commercial viability. In the meantime, fuel cells soldier on in the stationary power generation market, and are finding niches in forklifts and other short-range heavy vehicles, as well as in military applications.

But wait? Panasonic has started to deliver fuel cells that burn natural gas to produce heat and electricity in Japan and Bloom Energy is expected to come out of its hidey hole soon to talk about devices that pretty much do the same thing for industrial customers. By exploiting heat and power, these fuel cells can be 80 plus percent efficient. ...